Recently, various electronic information products, such as computers, have become highly popular among consumers and are widely applied to various fields. The demands for electronic information products lead to rapid development in electronic information techniques. It is a trend to develop electronic information products with increased operating speed and expanded access capacity. When operating at high speed, the components of the electronic information products would also produce a large amount of heat.
For example, among others, the central processing unit (CPU) of a computer produces the largest part of heat in the computer. The CPU would become slow in running when the heat produced and accumulated in the computer gradually increases. When the heat accumulated in the computer exceeds an allowable limit, the computer is subject to the danger of shutdown or even becoming seriously damaged. Moreover, to solve the problem of electromagnetic radiation, a case is used to enclose all the important computer components and elements therein. Therefore, it is very important to quickly dissipate the heat produced by the CPU and other heat-producing elements in the computer case.
Conventionally, a heat sink and a cooling fan are mounted atop the CPU to help in dissipating the heat produced by the CPU. A first side of the heat sink is formed of a plurality of radiating fins, while an opposite second side of the heat sink without radiating fin is in direct contact with the CPU to conduct the heat produced by the CPU to the radiating fins, from where the heat, is radiated into ambient air. Meanwhile, the cooling fan produces airflows to carry away the hot air surrounding the CPU and the heat sink, enabling quick dissipation of heat from the CPU.
Please refer to FIG. 1, which is an assembled sectional view of a conventional cooling fan 1. As shown, the cooling fan 1 includes a main body 11 having a centered locating seat 12 formed on an inner side thereof. The locating seat 12 has a hollow bearing housing 121 protruded therefrom. A bearing 13 is mounted in the bearing housing 121 and a coil 14 is fitted around the bearing housing 121. The cooling fan 1 further includes a fan hub 15, and a plurality of blades 151 spaced along an outer circumferential surface of the fan hub 15. A magnetic ring 152 is mounted to an inner circumferential surface of the fan hub 15 to magnetically interact with the coil 14. A rotary shaft 153 is provided on an inner side of the fan hub 15 to rearward extend through the bearing 13 and thereby hold the bearing in place.
The above-described cooling fan has some disadvantages in practical use thereof. For example, the coil 14 is forcedly pushed to locate around the bearing housing 121 in a tight-fit relation. Also, the bearing 13 is forcedly pushed into the bearing housing 121 to tightly fit therein. When forcedly pushing the coil 14 to locate it around the bearing housing 121, it is likely to cause detriment to the verticality of the bearing housing 121. And, when forcedly pushing the bearing 13 into the bearing housing 121, stress is concentrated at an end face of the bearing 13 to adversely affect the effective porosity of the bearing 13. As a result, noise will be produced while the cooling fan 1 operates and the usable life of the cooling fan 1 will be shortened. Moreover, when the rotary shaft 153 is first assembled to the bearing 13, an amount of lubricating oil is added to a rear end of the bearing 13. When the cooling fan 1 operates continuously to rotate the blades 151, the lubricating oil would move forward along the rotary shaft 153 and flow out of the bearing housing 121. As a result, the amount of the lubricating oil in the bearing 13 will reduce gradually to cause dry friction between the bearing 13 and the rotary shaft 153.
According to the aforesaid, the conventional cooling fan 1 has the following disadvantages: (1) The bearing housing tends to lose its verticality; (2) The bearing tends to lose its effective porosity; (3) The lubricating oil is likely to leak out; and (4) Noises are produced when the cooling fan operates and the usable life of the cooling fan is shortened.